A service like this one is all you need if you don’t want to end up like Homer Simpson and be “the dad who knew too little”. Zentracker makes it easy to keep tabs on your family by sending you SMSes, emails and Twitter messages with the location of your kids at all times. You can have Zentracker send you alerts when your kids enter or leave any place you have predefined (IE, their schools or clubs), so knowing they are where they are supposed to be is instantly done.
Zentracker uses Google Latitude to figure out where your kids are. There’s nothing to install on your smartphone to be updated on your kids’ whereabouts. And this also means Zentracker works with practically any smartphone that’s available.
The basic version of Zentracker (“Lite”) is free, and it can track up to 2 different mobile devices. For more than that (and for a full range of alerts) you have to go for the premium version of the service. That costs $8.95 per month, and you can upgrade to it whenever you want. You can also cancel the service at any time, there’s no contracts involved.
Zentracker.com In Their Own Words
Know where your kids are, get alerts when they move or reach destination.
Some Questions About Zentracker.com
In which other contexts could a service like this one be useful? 
